Chong, Geneva, Sara Simonson, Thomas Stohlgren, and Mohammed Kalkhan. 2001. Biodiversity: Aspen stands have the lead, but will nonnative species take over? Pp. 261-266 in Shepperd, Wayne, Dan Binkley, Dale Bartos, Thomas Stohlgren, and Lane Eskey, compilers. 2001. Sustaining Aspen in Western Landscapes: Symposium Proceedings. Proceedings RMRS-P-18. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 460 pp.
RELEVANT TO: FORESTS
INVASIVE SPECIES
WILDLIFE SPECIES
RESTORATION
DESCRIPTION
Ten vegetation types were sampled on 24 plots for plant species in a 54,000 hectare section of Rocky Mountain National Park, CO over four years. During one year butterfly species and abundance data were collected on four plots in six vegetation types: aspen, burned ponderosa, dry meadow, lodgepole pine, ponderosa pine, and wet meadow.
MAJOR FINDINGS
Although aspen stands cover only 2%-5% of Rocky Mountain National Park, and 1.2% of the study area, 150 plant species, which is 45% of all plants observed in all 24 plots, were found in the aspen type. Of these 150 plant species, 50 were unique to the aspen plots.
Of 49 butterfly species observed, 33 were seen in aspen, and seven were recorded only in aspen.
However, of the 42 nonnative plant species observed in the Park, 38 occurred in aspen, and 15 of those were found only in aspen.
Potential negative effects involve pollinator interactions between native and nonnative plants. "For example, we observed many butterflies on the flowers of musk thistle Carduus nutans L.) and Canada thistle (Cirsium arvense L.). Even though these nonnative species provide nectar, they are not suitable host plants for most butterfly larva[e], which often require specific native hosts. If nonnatives are being pollinated, this may increase their invasion success. In addition, many native plants are believed to be pollinator-limited [citation] even without competition for pollinators from nonnatives. If pollination of natives is reduced and results in decreased reproduction, this will exacerbate their displacement and could impact butterfly diversity by reducing the populations of required host plants" (p. 266).
Thus, it is not "biodiversity" per se (i.e., the number of species present) but native plant biodiversity that is important for maintaining native wildlife biodiversity and ecosystem functioning. Invasive plant species, for instance, can threaten the viability of native butterflies by displacing their larval hosts..
"...[M]anagers must be especially attentive to processes that encourage aspen regeneration or establishment (e.g., fire, disturbance) because these processes also facilitate nonnative species establishment" (p. 266).
QUESTIONS RAISED FOR THE THREE FORESTS
- Do current Forest management policies provide for protection of the native understory biodiversity of aspen?
- Do current Forest policies provide protection of the understory of all vegetation types (e.g., of sagebrush, aspen) as critical elements of support for wildlife biodiversity?
RELEVANCE TO FOREST MANAGEMENT
- Aspen management must consider aspen understory as an extraordinarily strong potential component of native plant and wildlife biodiversity, in addition to aspen support of bird diversity.
- Identification of aspen as a Management Indicator Species must take into account the importance of the condition of aspen understory and not merely presence of aspen.
- Processes used for restoration of aspen stands, and management of restored aspen stands must be such that invasive understory species are not aided